Const. Robb Costello would often tell his spouse that no matter what happened to him on the job, he would always come home.

On Friday, the Fredericton officer didn’t return.

Instead, police showed up at Jackie McLean’s home to tell her the 45-year-old was among four people killed in a shooting that took place in a quiet residential neighbourhood.

“This is the first day he did not come back home,” McLean, Costello’s common-law partner said. “I am having a really hard time envisioning my life without him.”

Fredericton Police Chief Leanne Fitch identified the dead officers — a seasoned warhorse and a recent recruit — as Lawrence Robb Costello, 45, a husband with four children, and Sara Mae Burns, 43, a wife with three children. They were the first officers to arrive at the scene of the early morning shooting and were shot as they rushed over to two people lying on the ground.

“This is the worst moment for any chief of police in any police agency to have to deliver this news,” Fitch said at a news conference.

The shooting left two more people dead — both civilians, a man and woman — but police have not released their identities. The accused gunman, a 48-year-old Fredericton man, is in hospital. He has not been identified.

Robb Costello.Fredericton Police

Costello, a detective known as Robb, worked on all manner of cases — from missing persons, robberies, street crimes, extortion, sex crimes — in Fredericton police’s major crimes unit and while seconded to the RCMP’s Internet child exploitation unit. He was a 20-year veteran of the force.

McLean said Costello would always leave for work with a smile.

“He loved being a police officer and he lived for being a police officer,” McLean said. “He is the only police officer who I have ever known who could write someone a ticket and have the person thank them after.”

Costello had two daughters from a previous relationship and McLean said he was also a role model for her two children.

“He is phenomenal as a father, he is very generous with his time and loved my children just as though they were his own,” she said. “We were very close to one another, we spent all of our free time together.”

Police and RCMP in Fredericton, N.B., on Friday, August 10, 2018.Keith Minchin/CP

In recent years, Costello drew the ire of local blogger and anti-police activist Charles LeBlanc. Costello and other fellow officers filed a criminal libel complaint against him over inflammatory internet postings and statements about the force. LeBlanc sued police saying Costello filed a request for information to LeBlanc’s internet service provider as part of a previous libel investigation that mistakenly stated it was a child sexual exploitation investigation.

In an online video posted soon after the shooting, LeBlanc said he was woken by a police officer wondering if he might have been involved in the shooting.

Const. Sara Burns grew up in Fredericton and joined the local police force in 2015, soon after graduating from the Atlantic Police Academy.

Burns went into policing after earning a bachelor of arts degree from Fredericton’s St. Thomas University with a major in criminology in 2014, according to city records. She graduated Fredericton High School in 1994.

When she was sworn in as an officer, her husband, Steven Burns, founder of Fredericton IT company Bulletproof, praised her dedication; she returned to school to get her degree at the age of 35 while she helped raise their three sons. She then had to leave home for six months to attend the Atlantic Police Academy in Prince Edward Island.

Posting on Facebook, she trumpeted her pride of being an officer during police week and shared her interest in helping the community through charity, youth and mental health supports and sport.

Burns told a newspaper in 2015 that she saw policing as a demanding career.

“(Policing) is something that I think challenges you physically, mentally and socially; you need to be aware of those components,” she told the Journal Pioneer newspaper. “It’s a really challenging field and to survive you need to keep all of those in check.”

Earlier this year, Burns narrowly missed being hit by a knife thrown at her during a standoff with a barricaded man after three of her colleagues were hit with bear spray when entering an apartment.

“Our hearts are broken by the murder of our two brave police officers. In this time of shock and grief, let us all protect their families,” Fredericton’s mayor, Mike O’Brien, said on Twitter. “Two civilians also tragically lost their lives today. Our city sends its love and support to all. We grieve as one.”

Awful news coming out of Fredericton. My heart goes out to everyone affected by this morning’s shooting. We’re following the situation closely.

The Fredericton Fire Department sends sincere condolences to the families and colleagues of two #Fredericton Police Officers who were lost in the line of duty today. We stand with you at this difficult time. pic.twitter.com/4vgPlz5zuk